The non-LTR (long terminal repeat) retrotransposon L1Tc from Trypanosoma cruzi codes for a protein with RNase H activity
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Rodríguez Heras, SaraEditorial
Elseivier
Fecha
2002Referencia bibliográfica
Olivares M, García-Pérez JL, Thomas MC, Heras SR, López MC. The non-LTR (long terminal repeat) retrotransposon L1Tc from Trypanosoma cruzi codes for a protein with RNase H activity. J Biol Chem. 2002 Aug 2;277(31):28025-30. doi: 10.1074/jbc.M202896200
Patrocinador
This work was supported by BFM2000-1381 and partially by SAF- 2001-3533 from Plan Nacional I D I (Ministerio de Ciencia y Tecnologı ´a), Spain. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.Resumen
The deduced amino acid sequence of the region downstream
of the reverse transcriptase (RT) motif of the
Trypanosoma cruzi L1Tc non-LTR retrotransposon
shows a significant homology with the sequence coding
for proteins with RNase H activity from different organisms
and retroelements. The 25-kDa His6-tagged recombinant
protein bearing only the L1Tc RNase H domain,
named RHL1Tc, exhibits RNase H activity as measured
on the [3H]poly(rA)/poly(dT) hybrid used as substrate as
well as on specific homologous and heterologous
[32P]RNA/DNA hybrids. The mutation of the conserved
aspartic acid at position 39 of the enzyme catalytic site,
but not of the serine at position 56 (non-conservative
amino acid), abolishes protein RNase H activity. The
RNase H activity of the RHL1Tc protein is Mg2 -dependent,
and it is also active in the presence of the Mn2 ion.
The optimal condition of RNase H activity is found at pH
8 and 37 °C, although it also has significant enzymatic
activity at 19 °C and pH 6. However, it cannot be excluded
that the RNase H activity level and its optimal
conditions may be different from that of a protein containing
both RT and RNase H domains.